I did some research on the weekend. The WPS using Apple Extreme doesn't work because it clones only the SSID and not the password. The Extreme generates a random, very complex PW. Apple explains that this is done to increase security. The Extreme WPS function will work for some devices like printers or other items that don't require you to enter a password.
This means that I had to go into the Admin functions of the "Extender", which was fairly easy once I found the instructions. Since the SSID had already been cloned, all I had to do was change the PW for the 2.4 and 5 GHz bands and I was off to the races.
I did this by connecting the "extender" directly to my computer via an ethernet cable and typing the appropriate URL for the device into a browser. There are all sorts of things you can do in the Admin functions, like setting access times for various devices, turning the LEDs on/off at various times, etc. Most people are probably already aware of all this "router functionality." Previously I had no need for any of this.
So, what was the end result? Before I installed the Powerline Adapter I was getting about 2-5 mbps down for WiFi in my basement. I'm now getting 70-90 mbps down and 10 up via WiFi. (I get 95/10 via Ethernet) On my main floor where I used to get around 30 down, I'm now getting 60-80 down, 10 up. (I'm paying Rogers for 75/10 service.) I'm a happy camper.
I hope that all this research and discussion assists others who are interested in Powerline Adapters.
PS. I'm not sure how fast these Powerline Adapters would be on higher Internet speeds - it may depend on the electrical circuitry in your home. Do not expect to get Gigabit speeds. For example, the following is from their website:
The TL-WPA8630 utilizes 802.11ac Wi-Fi to deliver dual band connections with combined speeds of up to 1350Mbps, including 867Mbps on the 5GHz band and 450Mbps on the 2.4GHz band.
For example, in some cases you may only get half that, but that should be more than adequate for most people... It would be interesting to hear back from people who have higher internet speeds and have these devices. (if you have different devices, please provide make/model)